Device and method for ablation of cardiac tissue

ABSTRACT

Methods for delivering precise amounts of fluid into cardiac tissue for the purpose of facilitating ablation of the tissue along a desired lesion line. One method injects fluid through a hollow needle. The injected fluid can be a highly conductive fluid injected in conjunction with radiofrequency ablation to create an ablative virtual electrode. The injected conductive fluid can provide deeper and narrower conduction paths and resulting lesions. Radiofrequency ablation can be performed at the same time as the fluid injection, using the injection device as an electrode, or subsequent to the fluid injection, using a separate device. In some methods, the injected fluid is a protective fluid, injected to protect tissue adjacent to the desired lesion line. Fluid delivery can be endocardial, epicardial, and epicardial on a beating heart. The present methods find one use in performing maze procedures to treat atrial fibrillation.

RELATED APPLICATIONS

[0001] The present application claims priority to U.S. provisionalpatent application serial No. 60/381,217, filed on May 16, 2002, titledDEVICE AND METHOD FOR ABLATION OF CARDIAC TISSUE, herein incorporated byreference in its entirety. The present invention is related commonlyassigned U.S. patent application Ser. No. ______/______,______, filed on______, titled DEVICE AND METHOD FOR NEEDLE-LESS INTERSTITIAL INJECTIONOF FLUID FOR ABLATION OF CARDIAC TISSUE [Docket number P-10134.00].

FIELD OF THE INVENTION

[0002] The present invention relates generally to the field of devicesfor cardiac surgery, and more specifically to devices for ablation ofcardiac tissue.

BACKGROUND OF THE INVENTION

[0003] The present invention is directed toward treatment oftachyarrhythmias, which are heart rhythms in which a chamber or chambersof the heart exhibits an excessively fast rhythm. In particular, thepresent invention is directed toward treatment of tachycardias, whichare due to the presence of ectopic foci within the cardiac tissue or dueto the presence of aberrant condition pathways within the cardiactissue.

[0004] There are many medical treatments that involve instances ofcutting, ablating, coagulating, destroying, or otherwise changing thephysiological properties of tissue. These techniques can be usedbeneficially to change the electrophysiological properties of tissue.For example, by ablation of cardiac tissue to cure various cardiacconditions. Normal sinus rhythm of the heart begins with the sinoatrialnode (or “SA node”) generating a depolarization wave front. The impulsecauses adjacent myocardial tissue cells in the atria to depolarize,which in turn causes adjacent myocardial tissue cells to depolarize. Thedepolarization propagates across the atria, causing the atria tocontract and empty blood from the atria into the ventricles. The impulseis next delivered via the atrioventricular node (or “AV node”) and thebundle of HIS (or “HIS bundle”) to myocardial tissue cells of theventricles. The depolarization of these cells propagates across theventricles, causing the ventricles to contract. This conduction systemresults in the described, organized sequence of myocardial contractionleading to a normal heartbeat.

[0005] Sometimes aberrant conductive pathways develop in heart tissue,which disrupt the normal path of depolarization events. For example,anatomical obstacles in the atria or ventricles can disrupt the normalpropagation of electrical impulses. These anatomical obstacles (called“conduction blocks”) can cause the electrical impulse to degenerate intoseveral circular wavelets that circulate about the obstacles. Thesewavelets, called “reentry circuits,” disrupt the normal activation ofthe atria or ventricles.

[0006] The aberrant conductive pathways create abnormal, irregular, andsometimes life-threatening heart rhythms, called arrhythmias. Anarrhythmia can take place in the atria, for example, as in atrialtachycardia, atrial fibrillation or atrial flutter. The arrhythmia canalso take place in the ventricle, for example, as in ventriculartachycardia.

[0007] The lesions used to treat atrial fibrillation, are typically longand thin and are carefully placed to interrupt the conduction routes ofthe most common reentry circuits. More specifically, the long thinlesions are used to create a maze pattern that creates a convoluted pathfor electrical propagation within the left and right atria. The lesionsdirect the electrical impulse from the SA node along a specified routethrough all regions of both atria, causing uniform contraction requiredfor normal atrial transport function. The lesions finally direct theimpulse to the AV node to activate the ventricles, restoring normalatrioventricular synchrony. Several surgical approaches have beendeveloped with the intention of treating atrial fibrillation. Oneparticular example is known as the “maze procedure,” as is disclosed byCox, J L et al. in “The surgical treatment of atrial fibrillation. I.Summary” Thoracic and Cardiovascular Surgery 101 (3), pp. 402-405(1991); and also by Cox, J L in “The surgical treatment of atrialfibrillation. IV. Surgical Technique”, Thoracic and CardiovascularSurgery 101 (4), pp. 584-592 (1991), both of which are incorporated byreference herein in their entireties. In general, the “maze” procedureis designed to relieve atrial arrhythmia by restoring effective atrialsystole and sinus node control through a prescribed pattern of incisionsabout the tissue wall. In the early clinical experiences reported, the“maze” procedure included surgical incisions in both the right and theleft atrial chambers. However, more recent reports predict that thesurgical “maze” procedure may be substantially efficacious whenperformed only in the left atrium, such as is disclosed in Sueda et al.,“Simple Left Atrial Procedure for Chronic Atrial Fibrillation AssociatedWith Mitral Valve Disease” (1996), which is incorporated herein byreference in its entirety.

[0008] When modifying the electrophysiological properties of cardiactissue by ablation, or by other means of destroying tissue to createlesions, physicians must carefully place the lesions. Otherwise, tissuewill be unnecessarily destroyed. In addition, the heart is in closeproximity to nerves and other nervous tissue and the destruction of thistissue will result in severe harm to the patient. Anatomical methods areused to locate the areas to be ablated or otherwise modified. In otherwords, the physician locates key structures such as the mitral valveannulus and the pulmonary veins. Lesions are typically formed that blockpropagations near these structures. Additional lesions are then formedwhich connect these lesions and complete the so-called “maze pattern.”However, the exact lesion pattern, and number of lesions created, canvary from patient to patient.

[0009] The surgical “maze procedure” as performed in the left atriumgenerally includes forming vertical incisions from the two superiorpulmonary veins and terminating in the region of the mitral valveannulus, traversing the inferior pulmonary veins en route. An additionalhorizontal line also connects the superior ends of the two verticalincisions. Thus, the atrial wall region bordered by the pulmonary veinostia is isolated from the other atrial tissue. In this process, themechanical sectioning of atrial tissue eliminates the precipitatingconduction to the atrial arrhythmia by creating conduction blocks withinthe aberrant electrical conduction pathways.

[0010] Although successful at treating AF, the surgical maze procedureis quite complex and is currently performed by only a few skilledcardiac surgeons in conjunction with other open heart procedures. Toolsthat could reliably duplicate the Maze incisions by other means (e.g.radiofrequency, laser, microwave, ultrasound energy) will reduce thetime and invasiveness required for the maze procedure and make it moreaccessible to more surgeons. Problems faced by these methods, however,include (a) the creation of continuous, linear lesions in the atria forthe prevention of atrial fibrillation, (b) minimization of clotting andthromboembolism, (c) the effect of heat loss due to circulating blood,(d) minimization of lesion width and minimization of atrial debulking,(e) conforming to an irregular myocardial thickness, (f) adaptability toa variety of lesion geometries and (g) usefulness from either theendocardial surface of an open heart, or the epicardial surface of abeating heart.

[0011] Injection of alcohol into heart tissue has also been employed toablate cardiac tissue. Alcohol may be delivered to blood vesselssupplying the tissue to be ablated, as described in “TranscoronaryChemical Ablation of Arrhythmias”, by Nellens et al, Pace Vol. 15, pages1368-1373, September 1992. Alternatively, alcohol can be delivereddirectly to the tissue to be ablated by means of a needle insertedthrough a catheter, as described in “Chemical Ablation by SubendocardialInjection of Ethanol via Catheter—Preliminary Results in the Pig Heart”,by Weismuller et al, European Heart Journal, Volume 12, pages 1234-1239,1991.

SUMMARY OF THE INVENTION

[0012] This invention relates to a device and method for ablation ofcardiac tissue in which a hand-held instrument having a hollow needle isused to deliver precise amounts of liquids into cardiac tissue forpurposes of ablation of the tissue along a desired lesion line.

[0013] In one aspect of the invention, a reciprocating needle devicelike that disclosed in U.S. Pat. No. 4,204,438, which is incorporated byreference in its entirety, is used to repeatedly penetrate cardiactissue and deliver a cytotoxic agent to the cardiac tissue. Thecytotoxic agent is used to “draw” a lesion on the myocardium by therepeated introduction of the needle and injection of cytotoxic fluidwhile moving the tip of the device along the desired lesion pattern.Because of the motor-driven reciprocating action of the device, thelesion pattern can be completed rapidly by the surgeon. A manuallyoperated switch on the housing of the device is capable of energizingand de-energizing the device as desired by the operator and an eccentricdrive advances and retracts the needle from the housing. The depth ofneedle penetration can be adjusted to control the depth at which thecytotoxic fluid is delivered to the tissue but preferably the depth ofneedle penetration enables the cytotoxic fluid to be injected into thetissue so that it extends through the entire thickness of the tissue.The hollow needle is filled with the cytotoxic agent. The cytotoxicfluid can be loaded into the needle a little at a time or it can befilled by means of a fluid reservoir. The delivery of the fluid canoccur passively as the needle is inserted into the tissue or it can beactively injected into the tissue according to needle position. Thefluid delivery can be performed endocardially, epicardially, andepicardially on a beating heart.

[0014] In yet another aspect of the invention, a non-reciprocatingmetering needle assembly like that disclosed in U.S. Pat. No. 4,719,825,which is incorporated by reference in its entirety, is use to repeatedlypenetrate cardiac tissue and deliver a cytotoxic agent to the cardiactissue. After the hollow needle has been inserted into the myocardialtissue, the device is activated by the operator to deliver apredetermined, metered amount of the cytotoxic agent into themyocardium. The needle is then withdrawn from the cardiac tissue andadvanced to a second location along the desired lesion pattern where itis inserted into the myocardium and another predetermined metered amountof cytotoxic agent is dispensed into the myocardial tissue. In thismanner, the device is advanced stepwise along the desired lesion line bythe operator in order to complete the lesion.

[0015] In yet another aspect of the invention, a device as describedabove is utilized in combination with radiofrequency ablation. Theneedle can be connected to one pole of a radiofrequency generator whilethe other pole of the generator is connected to a large indifferentelectrode. Rather than a cytotoxic agent, the needle delivers aconductive liquid such as a saline solution that creates an ablativevirtual electrode when delivered into the tissue through the needle. Thedevice is advanced along a desired lesion line on the tissue as theneedle is advanced into and retracted from the tissue. Delivery of theconductive liquid and the ablative radiofrequency energy is synchronizedto form the virtual electrode and ablate the tissue along the desiredlesion line.

[0016] In yet another aspect of the invention, a device as describedabove is utilized in combination with a conventional radiofrequencyablation device such as the Cardioblate® pen sold by Medtronic, Inc.Rather than a cytotoxic agent, the needle delivers a conductive liquidsuch as a hypertonic saline solution to the tissue. The device isadvanced along a desired lesion line on the tissue as the needle isadvanced into and retracted from the tissue. Delivery of the conductiveliquid is made into the tissue along the desired lesion line. Theconductive tip of the Cardioblate pen is then drawn along the desiredlesion line while applying radiofrequency energy to the tissue. Thehypertonic saline solution that creates a low impedance electricalpathway to ground such that the resultant lesion is deeper and narrowerthan would normally result from the use of the conventionalradiofrequency ablation device.

[0017] In yet another aspect of the invention, a device as describedabove is utilized in order to deliver a protective fluid in order toprotect certain areas of cardiac tissue, such as tissue near vessels andvalves. For example, a hypotonic fluid can be used as a protective fluidin order to increase the electrical impedance of the tissue to beprotected relative to the surrounding tissues, essentially insulatingthe protected tissue from the electrical current of the radiofrequencyablation device. This aspect of the invention can be combined with oneor more of the other aspects of the invention in which a conductiveliquid is delivered to a first portion of cardiac tissue along a desiredlesion line and a protective fluid is delivered to a second portion ofcardiac tissue spaced apart from the desired lesion line. This can bereadily accomplished by a device having a plurality of spaced-apartneedles with centrally located needles delivering the conductive liquidand other needles on one or both sides of the centrally located needleswhich deliver the protective fluid. As the radiofrequency ablationdevice, such as the Cardioblate pen, is advanced along the desiredlesion line a narrower and deeper lesion would result with thistechnique.

[0018] In yet another aspect of the invention, a device as describedabove is utilized in order to deliver an ink or dye to the cardiactissue in order to identify the position of the lesion line on thecardiac tissue and to identify portions of tissue along the lesion linewhere the lesion has been completed. For example, the ink or dye can beadded to the cytotoxic fluid in order to identify portions of tissuewhich have received the cytotoxic fluid and that those portions create acomplete lesion along the desired lesion line. Alternatively, the ink ordye can be added to the conductive liquid in order to identify theportions of tissue which has been ablated by the radiofrequency energyof a virtual electrode. Again the completeness of the lesion line isindicated by the presence of the ink or dye. Alternatively, the ink ordye can be added to the conductive liquid in order to identify theposition of the desired lesion line so that the Cardioblate pen or otherradiofrequency ablation device can be guided along the line that hasbeen established by the delivery of the conductive fluid. In yet anotheraspect, the ink or dye can be thermochromic such that it changes colorwhen heated to a temperature which indicates that a lesion has beenformed by the application of radiofrequency energy. Typically,temperatures above about 50 to 55 degrees C. are required to cause celldeath in an ablative lesion made by radiofrequency ablation and thephotochromic material would preferably change color in that temperaturerange.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a perspective view of a prior art device suitable foruse in the present invention

[0020]FIG. 2 is a perspective view of a prior art device suitable foruse in the present invention.

[0021]FIG. 3 is a schematic view of a device with a reciprocating needleoperating according to the invention.

[0022]FIG. 4 is a side sectional view of a needle delivering a fluidinto tissue according to the invention.

[0023]FIG. 5 is a side sectional view of fluid delivered according tothe invention that has diffused into tissue near its point of delivery.

[0024]FIG. 6 is a side sectional view showing needles delivering fluidaccording to the invention into tissue at varying depths.

[0025]FIG. 7 is a side sectional view of a needle delivering fluidaccording to the invention during reciprocation of the needle.

[0026]FIG. 8 is a side view of a distal portion of a needle showingmultiple fluid openings for delivery of fluid according to the presentinvention.

[0027]FIG. 9 is a side sectional view of a lesion created by theapplication of radiofrequency energy according to the invention.

[0028]FIG. 10 is a fragmentary, schematic, side sectional view of alinear array of needles which can be used for delivering protectivefluid about a delivered cytotoxic and/or conductive fluid.

[0029]FIG. 11 is a schematic view of the heart showing various mazelesions that can be formed according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0030] The following detailed description should be read with referenceto the drawings, in which like elements in different drawings arenumbered identically. The drawings, which are not necessarily to scale,depict selected embodiments and are not intended to limit the scope ofthe invention. Several forms of the invention have been shown anddescribed, and other forms will now be apparent to those skilled in art.It will be understood that embodiments shown in drawings and describedbelow are merely for illustrative purposes, and are not intended tolimit the scope of the invention as defined in the claims which follow.

[0031] This invention relates to a device and method for ablation ofcardiac tissue in which a hand-held instrument having a hollow needle isused to deliver precise amounts of liquids into cardiac tissue forpurposes of ablation of the tissue along a desired lesion line. FIGS. 1and 2 show prior art devices suitable for the practice of the presentinvention. FIG. 1 shows a reciprocating needle device 1 as disclosed inU.S. Pat. No. 4,204,438. The reciprocating needle device 1 includes amotor housing 10 and a needle housing 12. The needle housing 12 has anopening 14 through which a needle reciprocates. The device 1 may be heldby hand by a surgeon and used to repeatedly penetrate cardiac tissue bya reciprocating action of the needle and deliver a cytotoxic agent tothe cardiac tissue. FIG. 2 shows a non-reciprocating metering needledevice 20 like that disclosed in U.S. Pat. No. 4,719,825. The meteringneedle device 20 has a barrel portion 22 that can be held by hand, a tipportion 24 through which a needle 26 extends and a switch 28. A surgeoncan advance the needle 26 into myocardial tissue and then deliver ametered amount of a cytotoxic agent from the needle 26 by activating theswitch 28 on the metering needle device 20. Some tattoo pens are alsobelieved suitable for practicing the present invention. The tattoo penspreferably provide a longer than conventional needle travel path andalso provide a stronger than conventional driving force for driving theneedle or needles through the longer path.

[0032] The cytotoxic agent is an agent which has cytotoxic propertiesand can be delivered as an injectable liquid or a liquid suspension.Preferably the cytotoxic substance has potent cytotoxic properties thatdestroys cell function without affecting protein structure andscaffolding. Also preferably, the cytotoxic agent has limited andcontrollable diffusion properties through extracellular spaces. Alsopreferably the cytotoxic agent has a fleeting effect such that thecompound washes out of the systemic circulation quickly. Alkylatingagents such as cytotaxan or melphalan or their active metabolites arepreferred.

[0033] The cytotoxic agent is used to “draw” a lesion on the myocardiumby the repeated introduction of the needle and injection of cytotoxicfluid while moving the tip of the device along the desired lesionpattern. FIG. 11 shows some possible generally linear lesion patterns110 that are capable of interrupting conductive pathways 112 and 114.

[0034] Referring now to FIGS. 3-5, a reciprocating needle device 30 canhave a reservoir 32 and a hollow, reciprocating needle 34 through whichthe fluid 36 can be delivered into myocardial tissue 38. The needle 34may be tapered to allow for easy penetration of the tissue 38 anddelivery of fluid 36 into the tissue 38. Following delivery of thefluid, the needle is withdrawn and the fluid 36 diffuses into the tissue38. Needles 34 a-34 c also represent varying depth needles includedwithin an array or linear array of needles. The needle array can beadvanced along the desired lesion path and the needles insertedtogether, insuring multiple fluid delivery depths along the path. Such aphased linear array of needles also can reduce the force required toenter the myocardium, relative to a constant dept array, as the time ofentry into the tougher outer layer occurs at different times.

[0035] Referring now to FIGS. 6-8, the depth of penetration for needles34 a-c can be adjusted to control the depth at which the cytotoxic fluid36 is delivered to the tissue 38 through injection ports or orifices 37.The needle 34 d can also be adjusted to deliver the cytotoxic fluid asthe needle 34 d is inserted and/or withdrawn in order to providedelivery of fluid 36 at various depths. Also, the needle may be providedwith injection ports or openings 42 which will deliver fluid from aplurality of side openings or ports along the length of the needle 34 e.The delivery of the fluid can therefore occur passively as the needle isinserted into the tissue or it can be actively injected into the tissueaccording to needle position.

[0036] Referring now to FIG. 9, the device can also be utilized incombination with radiofrequency ablation. An ablative lesion 44 can becreated in tissue 48 by a needle connected to a radiofrequency generator(not shown) as a conductive fluid 46 is delivered through the needle 49into the tissue 48. Rather than a cytotoxic agent, the needle delivers aconductive liquid such as a saline solution that creates an ablativevirtual electrode when delivered into the tissue through the needle. Thedevice is advanced along a desired lesion line on the tissue as theneedle is advanced into and retracted from the tissue. Delivery of theconductive liquid and the ablative radiofrequency energy can besynchronized to form the virtual electrode and ablate the tissue alongthe desired lesion line.

[0037]FIG. 10 illustrates a linear array of needles 50 including aninjection manifold 52. Linear array 50 includes outer needles 54, 56,58, and 60, and inner needles 62 and 64. Inner needles 62 and 64 are fedby a first fluid delivery lumen 66 while outer needles 54-60 are fed bya second fluid delivery lumen 68. The inner needles can deliver aconductive and/or cytotoxic fluid, while the outer needles can deliver aprotective fluid, described below.

[0038] Referring now to FIG. 11, some possible generally linear lesionpatterns 110 are shown that are capable of interrupting conductivepathways 112 and 114. The lesion patterns can be made as described aboveor in combination with a conventional radiofrequency ablation devicesuch as the Cardioblate pen sold by Medtronic, Inc. (not shown). Ratherthan a cytotoxic agent, the needle delivers a conductive liquid such asa hypertonic saline solution to the tissue. The device is advanced alonga desired lesion line 110 on the tissue as the needle is advanced intoand retracted from the tissue. Delivery of the conductive liquid is madeinto the tissue along the desired lesion line 110. The conductive tip ofthe Cardioblate pen is then drawn along the desired lesion line 110while applying radiofrequency energy to the tissue. The hypertonicsaline solution that creates a low impedance electrical pathway toground such that the resultant lesion is deeper and narrower than wouldnormally result from the use of the conventional radiofrequency ablationdevice.

[0039] A protective fluid can also be used when making the linearlesions 110 in order to protect certain areas of cardiac tissue, such astissue near vessels and valves like the pulmonary veins 116. Forexample, a hypotonic fluid can be used as a protective fluid in order toincrease the electrical impedance of the tissue to be protected relativeto the surrounding tissues, essentially insulating the protected tissuefrom the electrical current of the radiofrequency ablation device.Alternatively, the protective fluid can be a thermally protective fluidsuch as a chilled fluid which protects tissue adjacent to the intendedlesion from being overheated. This aspect of the invention can becombined with one or more of the other aspects of the invention in whicha conductive liquid is delivered to a first portion of cardiac tissuealong a desired lesion line and a protective fluid is delivered to asecond portion of cardiac tissue spaced apart from the desired lesionline. This can be readily accomplished by a device having a plurality ofspaced-apart needles with centrally located needles delivering theconductive liquid and other needles on one or both sides of thecentrally located needles which deliver the protective fluid, asdiscussed with respect to FIG. 10. As the radiofrequency ablationdevice, such as the Cardioblate pen, is advanced along the desiredlesion line a narrower and deeper lesion would result with thistechnique.

[0040] Also, the device as described above can be utilized in order todeliver an ink or dye to the cardiac tissue in order to identify theposition of the lesion line 110 on the cardiac tissue and to identifyportions of tissue along the lesion line 110 where the lesion has beencompleted. For example, the ink or dye can be added to the cytotoxicfluid in order to identify portions of tissue which have received thecytotoxic fluid and that those portions create a complete lesion alongthe desired lesion line. Alternatively, the ink or dye can be added tothe conductive liquid in order to identify the portions of tissue whichhas been ablated by the radiofrequency energy of a virtual electrode.Again the completeness of the lesion line is indicated by the presenceof the ink or dye. Alternatively, the ink or dye can be added to theconductive liquid in order to identify the position of the desiredlesion line so that the Cardioblate pen or other radiofrequency ablationdevice can be guided along the line that has been established by thedelivery of the conductive fluid. Dyes such as those used for tattoosare believed suitable, as are some tissue dyes. Toluene blue andmethylene blue are examples of dyes believed suitable for use in thepresent invention.

[0041] In yet another aspect, the ink or dye can be thermochromic suchthat it changes color when heated to a temperature which indicates thata lesion has been formed by the application of radiofrequency energy.Typically, temperatures above about 50 to 55 degrees C. are required tocause cell death in an ablative lesion made by radiofrequency ablationand the photochromic material would preferably change color in thattemperature range.

[0042] In still another aspect, the injected fluid can include a viscousenhancing agent or fluid added to reduce or retard fluid diffusion afterdelivery. Reducing the diffusion of a cytotoxic and/or conductive fluidcan reduce the width of the resulting lesion. Reducing the diffusion ofa protective fluid can maintain the protective fluid in a desiredposition adjacent the cytotoxic and/or conductive fluid, to serve itsprotective function. Viscous fluids such as dextrose or glycerol may beadded to increase the viscosity of a delivered fluid. The viscous fluidsor agents can provide a fluid viscosity of at least about twice that ofwater.

[0043] It will be appreciated by those skilled in the art that while theinvention has been described above in connection with particularembodiments and examples, the invention is not necessarily so limited,and that numerous other embodiments, examples, uses, modifications anddepartures from the embodiments, examples and uses are intended to beencompassed by the claims attached hereto. The entire disclosure of eachpatent and publication cited herein is incorporated by reference, as ifeach such patent or publication were individually incorporated byreference herein.

1. A method for ablation of myocardial tissue comprising: providing ahand-held instrument having a hollow needle; selecting a desired line ofablation on a surface of the tissue; applying the needle to the tissueat a portion of the desired line of ablation such that it penetrates thetissue; and delivering a predetermined amount of fluid into thepenetrated tissue to facilitate ablation of the tissue along the desiredlesion line.
 2. A method according to claim 1 wherein the needlereciprocates to repeatedly penetrate and deliver a fluid to themyocardial tissue along the desired line of ablation.
 3. A methodaccording to claim 1 wherein the fluid applied to the myocardial tissueis a cytotoxic agent applied in amount effective to ablate themyocardial tissue.
 4. A method according to claim 3 wherein cytotoxicagent draws a lesion on the myocardium by the repeated introduction ofthe needle and injection of cytotoxic fluid while moving the tip of thedevice along the desired lesion pattern.
 5. A method according to claim2 wherein the fluid is introduced into the needle by means of a fluidreservoir.
 6. A method according to claim 1 wherein delivery of thefluid is actively injected into the tissue according to the needleposition in the myocardial tissue.
 7. A method according to claim 1wherein the fluid is delivered to the myocardium in a predetermined,metered amount.
 8. A method according to claim 1 wherein the needle iswithdrawn from the myocardial tissue and advanced to a second locationalong the desired line of ablation where the needle is inserted into themyocardium and another amount of fluid is dispensed into the myocardialtissue.
 9. A method according to claim 1 also comprising the step ofapplying radiofrequency ablation through the needle.
 10. A methodaccording to claim 9 wherein the needle delivers a conductive liquid.11. A method according to claim 10 wherein the conductive liquid is asaline solution that creates an ablative virtual electrode whendelivered in combination with the application of radiofrequencyablation.
 12. A method according to claim 9 wherein the needle is movedalong the desired lesion line on the tissue as the needle is advancedinto and retracted from the tissue.
 13. A method according to claim 12wherein the liquid and the ablative radiofrequency energy aresynchronized to form a virtual electrode and ablate the tissue along thedesired lesion line.
 14. A method according to claim 1 also comprisingcompleting delivery of fluid along the desired lesion line andsubsequently applying to the desired lesion line radiofrequencyablation.
 15. A method according to claim 14 wherein the fluid is ahypertonic saline solution.
 16. A method according to claim 1 whereinthe fluid is a protective fluid which increases the electrical impedanceof the myocardial tissue.
 17. A method according to claim 16 wherein theprotective fluid is delivered to tissue near a heart valve.
 18. A methodaccording to claim 16 wherein the protective fluid is delivered totissue near a blood vessel.
 19. A method according to claim 16 whereinthe fluid is a hypotonic fluid.
 20. A method according to claim 1wherein the fluid comprises an ink or dye.
 21. A method according toclaim 20 wherein the fluid comprises a cytotoxic fluid.
 22. A methodaccording to claim 20 wherein the fluid comprises a conductive fluid.23. A method according to claim 20 wherein the fluid comprises aprotective fluid.
 24. A method according to claim 20 also comprisingvisually inspecting the ink or dye on the lesion line.
 25. A methodaccording to claim 20 wherein the ink or dye changes color at apredetermined temperature.
 26. A method according to claim 1, whereinthe fluid comprises a viscosity enhancing agent.
 27. A method accordingto claim 1, wherein the delivering is performed epicardially.
 28. Amethod according to claim 1, wherein the delivering is performedendocardially.
 29. A method according to claim 1, wherein the providedhand-held instrument further comprises a needle array comprising aplurality of hollow needles in addition to the hollow needle, where inthe applying includes applying the plurality of needles to penetrate thetissue, wherein the delivering includes delivering fluid into thepenetrated tissue through the plurality of needles.
 30. A method forablation of myocardial tissue comprising: providing a hand-heldinstrument having an injection port for injecting fluid into myocardialtissue; selecting a desired line of ablation on a surface of the tissue;applying the injection port to the tissue at a portion of the desiredline of ablation; delivering a predetermined amount of fluid into themyocardial tissue to facilitate ablation of the tissue along the desiredlesion line.
 31. A method according to claim 30 wherein the fluidapplied to the myocardial tissue includes a cytotoxic agent applied inamount effective to ablate the myocardial tissue.
 32. A method accordingto claim 30 wherein the fluid is delivered to the myocardium in apredetermined, metered amount.
 33. A method according to claim 30wherein the injection device is advanced to a second location along thedesired line of ablation and another amount of fluid is dispensed intothe myocardial tissue.
 34. A method according to claim 30 alsocomprising the step of applying radiofrequency ablation through theinjection device.
 35. A method according to claim 34 wherein theinjection device delivers a conductive liquid.
 36. A method according toclaim 35 wherein the conductive liquid is a saline solution that createsan ablative virtual electrode when delivered in combination with theapplication of radiofrequency ablation.
 37. A method according to claim34 wherein the injection port is moved along the desired lesion line onthe tissue as the fluid is injected into the tissue.
 38. A methodaccording to claim 37 wherein the liquid and the ablative radiofrequencyenergy are synchronized to form a virtual electrode and ablate thetissue along the desired lesion line.
 39. A method according to claim 30also comprising completing delivery of fluid along the desired lesionline and subsequently applying to the desired lesion line radiofrequencyablation.
 40. A method according to claim 39 wherein the fluid is ahypertonic saline solution.
 41. A method according to claim 30 whereinthe fluid is a protective fluid which increases the electrical impedanceof the myocardial tissue.
 42. A method according to claim 41 wherein theprotective fluid is delivered to tissue near a heart valve.
 43. A methodaccording to claim 41 wherein the protective fluid is delivered totissue near a blood vessel.
 44. A method according to claim 41 whereinthe fluid is a hypotonic fluid.
 45. A method according to claim 30wherein the fluid comprises an ink or dye.
 46. A method according toclaim 45 wherein the fluid comprises a cytotoxic fluid.
 47. A methodaccording to claim 45 wherein the fluid comprises a conductive fluid.48. A method according to claim 45 wherein the fluid comprises aprotective fluid.
 49. A method according to claim 45 also comprisingvisually inspecting the ink or dye on the lesion line.
 50. A methodaccording to claim 30 wherein the ink or dye changes color at apredetermined temperature.
 51. A method according to claim 30, whereinthe fluid comprises a viscosity enhancing agent.
 52. A method accordingto claim 30, wherein the delivering is performed epicardially.
 53. Amethod according to claim 30, wherein the delivering is performedepicardially on a beating heart.
 54. A method according to claim 30,wherein the delivering is performed endocardially.